Random polyester-phosphonates and random polycarbonatophosphonates can be prepared by melt condensation from bisphenol, phosphonic acid ester monomers and carboxylic acid ester monomers or from bisphenol, phosphonic acid ester monomers and diphenyl carbonate monomers (See for example, DE-OS (German Published Specification) Nos. 2,925,206 and 2,925,208). The polymers made using these methods are random (or statistical) mixtures of the monomers and these materials do not have good toughness compared to polycarbonate alone.
In U.S. Pat. No. 4,782,123 coplyhosphonates are prepared by extrusion of solutions of aromatic polyesters and aromatic polyphosphonates at elevated temperatures to give copolyphosphonates. This process requires the use and then subsequent removal of organic solvent from the product mixture. This extra process and the attendant disposal of the organic solvent make this process undesirable and costly.
In U.S. Pat. No. 4,762,905 thermoplastic polyphosphonatocarbonates are prepared by polycondensation of at least one aromatic dihydroxy compound with a diaryl carbonate and a phosphonic acid diaryl ester in the presence of a basic polycondensation catalyst with heating under reduced pressure. These methods, again, provide statistical mixing of carbonate and phosphonate monomers in the polymer. Where blocks of phosphonate or carbonate occur in the polymer, it is difficult to control their length. The block polymer prepared from the monomers does not have good toughness compared to the polycarbonate or a good limiting oxygen index compared to the polyphosphonate.
In U.S. Pat. No. 4,508,890 thermoplastic polyphosphonatocarbonates are prepared by polycondensation of at least one aromatic dihydroxy compound with a diaryl carbonate and a phosphonic acid diaryl ester in the presence of a neutral catalyst. Neutral catalysts are expensive and do not provide control over polyhosphonate block size in the block polymer. Also, where the neutral catalysts remains in the final polymer product, it may cause problems such as increased haze, reduced hydrolytic stability, reduced optical transparency, increased color and can catalyze the thermal degradation of the polymer during use at elevated temperature. The block polymer prepared from the monomers and neutral catalyst does not have good toughness compared to the polycarbonate or a good limiting oxygen index compared to polyphosphonate.